1. Field of the Invention
This invention relates to a solid state image pick-up device contained in an electronic still camera, a video camera or the like.
2. Related Background Art
As a solid state image pick-up device used in an electronic still camera, use has heretofore been made of an interline transfer type CCD capable of temporarily storing light signal charges in the other portion than a light-receiving portion, and the electronic shutter function in this interline transfer type CCD is performed by the use of an overflow drain (hereinafter referred to as "OFD") and an overflow control gate (hereinafter referred to as "OFCG") for controlling the accumulation and discharge of light signal charges in the light-receiving portion (Japanese Laid-open patent application No. 44271/1981).
That is, OFD and OFCG have the function of discharging excess charges so that the blooming phenomenon may not occur when excessive light signal charges are produced in the light-receiving portion, and further, by adjusting the OFCG voltage, the amount of signal charges which can be accumulated in the light-receiving portion can be controlled. So, as an electronic shutter, the OFCG voltage is controlled in time to a state in which signal charges cannot be accumulated in the light-receiving portion and to a state in which normal accumulation is possible, whereby the exposure time of the light-receiving portion may be determined and the shutter function can be realized by the solid state image pick-up device itself.
In recent years, however, due to the high resolution of the solid state image pick-up device, the number of light-receiving portions has increased, and with such increase in the number of light-receiving portions, the simplification of the transfer gate and the OFCG structure has been achieved and there has been the advent of an interline transfer type CCD which cannot singly control OFCG.
With regard to such a solid state image pick-up device which cannot singly control OFCG, it would involve great difficulties to realize the shutter function by the solid state image pick-up device itself using the conventional control of the OFCG voltage, and this has led to a problem that the conventional mechanical shutter must be resorted to.
Also, a video camera capable of operating at a high shutter speed has the advantages that the dynamic resolution during normal operation is improved and that clear-cut images free of blur are obtained during slow motion reproduction or still reproduction, but yet it has suffered from a disadvantage that the necessity of providing a mechanical rotary shutter in front of the image pick-up device makes the entire apparatus bulky and heavy and accordingly incovenient to handle.